1. Field of the Invention
The present invention relates to a substrate used for immersion lithography process used in an immersion lithography process and a method of manufacturing thereof, and immersion lithography using thereof.
2. Description of the Related Art
In the filed of manufacturing various devices such as semiconductors and magnetic heads, photolithography has been widely used in a forming process of fine patterns. Photolithography is generally a method of forming a photo-sensitive film (photoresist film) on a substructure and selectively exposing and developing the photoresist film using a photomask. By photolithography, a pattern shape of a photomask is transcribed to the photoresist film so that patterning is performed on the photoresist film in reflection of the pattern shape.
With respect to the resolution of photolithography, further improvement is desirable due to a rapid size reduction of the device in recent years. Therefore immersion lithography has attracted attention as an exposure method capable of improving the resolution. Immersion lithography is a method of exposing such that liquid (namely, immersion liquid) fills between a projection lens of an exposure device (stepper) and a photoresist film. In immersion lithography, the resolution additionally improves due to contribution of refractive index of the immersion liquid in comparison with the case of exposing in air without using the immersion liquid.
With respect to immersion lithography, several related techniques have already been proposed. Specifically, in case of using water-type immersion liquid, hydrophobic technique of oxidizing the surface of the photoresist film in order to prevent occurrence of bubbles (micro-bubbles) in the immersion liquid has been known (for example, refer to Japanese Unexamined Patent Publication No. 2006-108564).
Also, a technique to improve a specific problem in immersion lithography, that is, an antinomic problem occurred due to a contact of the photoresist film with the immersion liquid has been known (for example, refer to Japanese Unexamined Patent Publication No. 2006-019742). Specifically, when focusing on the surface tension of the photoresist film, if the surface tension is low (wetting of the immersion liquid is poor), immersion liquid hardly leaks out from the exposed area but bubbles are easily produced in the immersion liquid. On the other hand, if the surface tension of the photoresist film is high (wetting of the immersion liquid is good), bubbles are hardly produced but the immersion liquid easily leaks out from the exposed area. Thus after supplying the immersion liquid on the photoresist film, an interface activating gas substance is supplied to the immersion liquid. By forming a mixed substance having a low surface tension, between the photoresist film and the immersion liquid, the surface tension gradient pulling the immersion liquid is generated.